The present invention relates to a rotation information detector for detecting rotation information including information on a rotational direction of an internal combustion engine, and a signal generator used in the detector.
In many vehicles such as scooters, snowmobiles, or buggies that value simplicity of use, a two cycle internal combustion engine is frequently used as a driving source. Such vehicles often use a variable speed type transmission of a centrifugal clutch type, which does not have a back-up gear, as a transmission provided between a crankshaft of the engine and a driving wheel. However, even a vehicle that uses such a simple transmission is desirably backed using an engine when a body is heavy or a snowmobile having crashed into snow is backed.
Thus, it has been supposed that when a two cycle internal combustion engine is used as a driving source, a feature of the two cycle internal combustion engine that allows rotation in both forward and reverse directions is used to allow reversal of a rotational direction of the engine in accordance with a driver""s instruction, thereby permitting the engine to be driven in both forward and reverse rotation states.
A known method for reversing a rotational direction of a two cycle internal combustion engine is such that in accordance with a driver""s reversal instruction, a rotational speed of the engine is lowered to a set rotational speed below an idling speed by fuel cut, engine misfire, or ignition timing delay, the ignition timing is then excessively advanced to reverse the rotational direction of the engine, and after the reversal of the rotational direction of the engine is confirmed, the ignition timing of the engine is shifted to timing suitable for keeping driving of the engine with the rotational direction reversed.
For reversing the rotational direction of the internal combustion engine by such a method to drive the engine in the forward and the reverse rotation states, obtaining information on the rotational direction of the engine is essential.
An internal combustion engine built in a vehicle using a transmission with a gear for backing up sometimes requires obtaining information on the rotational direction of the engine in order to prevent the reverse rotation of the engine.
When the ignition timing of the internal combustion engine is controlled by a microprocessor, a predetermined rotational angle position (crank angle position) of a crankshaft of the engine is set as a reference position, the ignition timing is arithmetically operated relative to timing at which the rotational angle position of the crankshaft corresponds to the reference position, and measuring the arithmetically operated ignition timing is started when the rotational angle position of the crankshaft corresponds to the reference position. Thus, in this case, it is necessary to be able to detect that the rotational angle position of the crankshaft corresponds to the reference position.
Further, when the engine runs at extremely low speed, the rotational speed of the crankshaft varies minutely due to changes in strokes of the engine, and precise measurement of the ignition timing arithmetically operated by the microprocessor is difficult. Thus, when the engine runs at extremely low speed, it is preferable that the ignition is not performed at the ignition timing arithmetically operated by the microprocessor, but is performed at predetermined fixed ignition timing. In the case where the ignition is performed at the fixed ignition timing when the engine runs at extremely low speed (when the rotational angle position of the crankshaft corresponds to a fixed ignition position), it is necessary to be able to detect that the rotational angle position of the crankshaft corresponds to a position corresponding to the ignition timing when the engine runs at extremely low speed.
When the ignition timing is controlled by the microprocessor, the rotational speed of the engine is calculated by measuring time for the crankshaft to rotate by a fixed angle.
In order to obtain various rotation information such as the information on the rotational direction of the internal combustion engine, the information on the reference position of the crankshaft, the information on the ignition position when the engine runs at extremely low speed, or the information on the rotational speed, a signal generator is widely used that comprises a rotor in the form of an inductor having a reluctor and provided to rotate in synchronization with the engine, and a sensor that detects a leading edge and a trailing edge in a rotational direction of the reluctor of the rotor to generate a leading edge detection pulse and a trailing edge detection pulse having different polarities.
A known method for obtaining information on a rotational direction of an engine using such a signal generator is disclosed in U.S. Pat. No. 5,794,574. In the prior art, two sensors are placed at a predetermined interval around a rotor in the form of an inductor having two reluctors, and information on whether the engine rotates forward or reversely is obtained using a feature that a relationship between a length of a time period between when one of the sensors detects a trailing edge of one reluctor of the rotor to generate a trailing edge detection pulse and when the other sensor detects a leading edge of one reluctor to generate a leading edge detection pulse, and a length of a time period when the other sensor detects a trailing edge of the other reluctor to generate a trailing edge detection pulse and when one sensor detects the leading edge of one reluctor to generate the leading edge detection pulse differs in forward rotation and in reverse rotation of the engine.
When the rotational speed of the crankshaft of the internal combustion engine is constant, as the method disclosed in the above U.S. Patent, comparing generation intervals of particular pulses allows the rotational speed of the engine to be reliably discriminated. However, when the engine runs at extremely low speed, the rotational speed of the crankshaft varies during one rotation of the crankshaft due to changes in strokes of the engine, thus the above described method may cause erroneous discrimination of the rotational direction.
For a multi-cylinder internal combustion engine having two or more cylinders, provided on a rotor side with a reluctor corresponding to each cylinder of the engine, it is necessary to obtain information (cylinder discrimination information) for discriminating which cylinder a series of pulses, generated by a sensor detecting a leading edge and a trailing edge of a series of reluctors, corresponds to, but the signal generator disclosed in the above U.S. patent cannot provide such cylinder discrimination information.
Therefore, an object of the invention is to provide a signal generator for an internal combustion engine capable of generating a signal for obtaining precise rotation information including information on a rotational direction of an engine and cylinder discrimination information even when the engine runs at extremely low speed at which a rotational speed of a crankshaft widely varies.
Another object of the invention is to provide a rotation information detector for an internal combustion engine that uses the above described signal generator to obtain rotation information including information on a rotational direction of an engine and cylinder discrimination information.
The invention provides a signal generator used for detecting rotation information including information on a rotational direction of a multi-cylinder internal combustion engine having two or more cylinders and cylinder discrimination information, and a rotation information detector using the signal generator.
The signal generator according to the invention comprises: a rotor in the form of an inductor having a first series of reluctors as many as cylinders of the internal combustion engine, that are provided correspondingly to each cylinder of the internal combustion engine and are rotated together with a crankshaft around a central axis of the crankshaft of the internal combustion engine, and a second series of at least one reluctor that is provided in a position shifted axially along the crankshaft relative to the first series of reluctors and is rotated together with the first series of reluctors; a first sensor that detects a leading edge and a trailing edge in a rotational direction of the first series of reluctors of the rotor to generate a leading edge detection pulse and a trailing edge detection pulse having different polarities; and a second sensor that detects a leading edge and a trailing edge in a rotational direction of the second series of reluctor of the rotor to generate a leading edge detection pulse and a trailing edge detection pulse having different polarities, wherein polar arc angles of the first and the second series of reluctors, a positional relationship between the first and the second sensors, and a positional relationship between the first and the second series of reluctors are set so that the second sensor detects the leading edge or the trailing edge of the second series of one reluctor to generate one pulse while the first sensor sequentially detects at least one leading edge and at least one trailing edge of the first series of reluctors to generate the leading edge detection pulse and the trailing edge detection pulse.
In the invention, each of the first series of reluctors is provided correspondingly to each cylinder of the engine. xe2x80x9cProviding each reluctor correspondingly to each cylinderxe2x80x9d means that each reluctor is placed in a position suitable for generating a pulse, from the first sensor, that includes crank angle information required for controlling each cylinder, when the first sensor detects the reluctor corresponding to each cylinder.
For example, when ignition timing of the internal combustion engine is controlled relative to a rotational speed, a pulse generated in a fixed crank angle position by the signal generator is sometimes used as a signal for determining the ignition timing (fixed ignition signal) when the internal combustion engine starts or runs at extremely low speed at which the precise ignition timing arithmetically operated by the microcomputer cannot be measured. In such a case, the reluctor corresponding to each cylinder is placed so that it is generated the pulse that may be used as the fixed ignition signal for each cylinder when the first sensor detects the edge of the reluctor corresponding to each cylinder.
When ignition timing of a multi-cylinder internal combustion engine, at which a series of cylinders are sequentially ignited at crank angle positions at equal mechanical angle intervals, is controlled, the first series of reluctors as many as the cylinders of the engine are basically placed at equal angle intervals in order to generate the fixed ignition signal for each cylinder from the first sensor. However, in this case, the invention is not limited to the case where the first series of reluctors are placed at precisely equal angle intervals, but the positions of some of the first series of reluctors may be shifted from the positions where all the first series of reluctors are placed at equal intervals without the ignition timing when each cylinder of the engine starts and runs at extremely low speed departing from an acceptable variation range.
For example, when ignition timing of a two cylinder internal combustion engine is controlled, a first series of two reluctors are preferably provided at a 180xc2x0 interval, but an angle between the two reluctors may be slightly shifted from 180xc2x0 without a generation position of a fixed ignition signal for determining ignition timing of each cylinder departing from an acceptable range. That is, in this case, the first series of two reluctors may be provided at a substantially 180xc2x0 interval.
As described above, the signal generator is comprised so as to include the first series of reluctors and the second series of reluctor; the first sensor that detects the leading edge and the trailing edge of the first series of reluctors to generate the leading edge detection pulse and the trailing edge detection pulse; and the second sensor that detects the leading edge and the trailing edge of the second series of reluctor to generate the leading edge detection pulse and the trailing edge detection pulse, wherein the second sensor detects the leading edge or the trailing edge of the second series of one reluctor to generate one pulse while the first sensor sequentially detects at least one leading edge and at least one trailing edge of the first series of reluctors to generate the leading edge detection pulse and the trailing edge detection pulse. Thus, a difference occurs in a phase relationship between the pulse generated by the first sensor and the pulse generated by the second sensor in forward rotation of the crankshaft, and in a phase relationship between the pulse generated by the first sensor and the pulse generated by the second sensor in reverse rotation of the crankshaft. This is because reversal of the rotational direction of the internal combustion engine causes the leading edge detection pulse and the trailing edge detection pulse to change their generation positions.
Thus, in the signal generator according to the present invention, the difference occurs in the phase relationship between the output pulse of the first sensor and the output pulse of the second sensor in the forward rotation and in the reverse rotation of the internal combustion engine. Therefore, detecting various events caused by the difference in the phase relationship may provide the rotation information such as the information on the rotational direction of the engine, or the information on the cylinder corresponding to the pulse generated by the first sensor.
To find the difference in the phase relationship between the output pulse of the first sensor and the output pulse of the second sensor, it is basically sufficient to observe order of generation of the leading edge detection pulse and the trailing edge detection pulse by both sensors, and measuring time between the pulses is not required. Thus, the above described way of obtaining the information on the rotational direction of the engine allows the precise information on the rotational direction of the engine to be obtained even when the engine runs at extremely low speed at which the rotational speed of the crankshaft varies.
Further, in the signal generator comprised as described above, the second sensor generates one pulse while the first sensor detects the reluctor corresponding to a particular cylinder to sequentially generate the leading edge detection pulse and the trailing edge detection pulse, thus discriminating whether the second sensor generates one pulse while the first sensor sequentially generates the leading edge detection pulse and the trailing edge detection pulse provides cylinder discrimination information on which cylinder of the internal combustion engine the leading edge detection pulse and the trailing edge detection pulse sequentially generated by the first sensor correspond to.
Thus, the rotation information detector for the multi-cylinder internal combustion engine may be comprised by achieving rotational direction discrimination means for obtaining the information on the rotational direction from the output pulse of the signal generator and cylinder discrimination means for obtaining the cylinder discrimination information from the output pulse of the signal generator, which are provided by inputting the pulse output by the signal generator to a CPU to cause the CPU to execute a predetermined program.
The rotational direction discrimination means may be comprised so as to discriminate the rotational direction of the engine using a feature that the phase relationship between the leading edge detection pulse and the trailing edge detection pulse generated by the first sensor and the leading edge detection pulse and the trailing edge detection pulse generated by the second sensor differs depending on the rotational direction of the engine.
Also, the cylinder discrimination means may be comprised so as to discriminate that, when the second sensor generates one pulse while the first sensor sequentially generates the leading edge detection pulse and the trailing edge detection pulse, the leading edge detection pulse and the trailing edge detection pulse sequentially generated by the first sensor correspond to the particular cylinder of the internal combustion engine.
The difference in the phase relationship between the pulses generated by the first and the second sensors in the forward rotation and in the reverse rotation of the engine may be detected from changes in various events caused by the changes in the phase relationship between the output pulses of the first and the second sensors due to the reversal of the rotational direction.
For example, the rotational direction discrimination means may be comprised so as to obtain the information on the rotational direction of the engine using a feature that, when the rotational direction of the internal combustion engine is reversed, a polarity of one pulse (the leading edge detection pulse or the trailing edge detection pulse) generated by the second sensor between when the first sensor generates the leading edge detection pulse and when the first sensor generates the trailing edge detection pulse is reversed (the leading edge detection pulse and the trailing edge detection pulse generated by the second sensor change their generation positions in the forward rotation and in the reverse rotation of the engine).
In addition, the rotational direction discrimination means may be comprised so as to obtain the information on the rotational direction of the engine using a feature that the number of leading edge detection pulses or the trailing edge detection pulses generated by the second sensor between when the first sensor generates one leading edge detection pulse and when the first sensor generates a next leading edge detection pulse differs depending on the rotational direction of the engine
Further, the rotational direction discrimination means may be comprised so as to obtain the information on the rotational direction of the engine using a feature that the number of leading edge detection pulses or the trailing edge detection pulses generated by the second sensor between when the first sensor generates one trailing edge detection pulse and when the first sensor generates a next trailing edge detection pulse differs depending on the rotational direction of the engine.
In the signal generator comprised as described above, a position of each pulse generated by each sensor in the forward rotation and in the reverse rotation of the engine is fixed, thus recognizing the pulse generated by each sensor may provide the information on the rotational angle position of the engine, and besides, measuring an elapsed time between generation times of the particular pulses (a time required for fixed angular rotation of the crankshaft) may provide the information of the rotational speed of the engine.
In the above description, the rotational direction of the internal combustion engine is discriminated using the feature that the phase relationship between the leading edge detection pulse and the trailing edge detection pulse generated by the first sensor and the leading edge detection pulse and the trailing edge detection pulse generated by the first sensor differs depending on the rotational direction of the crankshaft. However, the rotational direction of the internal combustion engine may be discriminated based on a phase relationship between a pulse with one polarity (the leading edge detection pulse or the trailing edge detection pulse) generated by the first sensor and the leading edge detection pulse and the trailing edge detection pulse generated by the second sensor.
Further, it may be discriminated which cylinder of the internal combustion engine the pulse generated by the first sensor corresponds to, from a polarity or the number of pulses generated by the second sensor between when the first sensor generates the pulse with one polarity and when the first sensor generates a pulse with the same polarity again.
When comprised as described above, the rotation information including the information on the rotational direction of the engine and the cylinder discrimination information can be obtained simply by reading in the CPU three pulses: one of the leading edge detection pulse and the trailing edge detection pulse generated by the first sensor, and the leading edge detection pulse and the trailing edge detection pulse generated by the second sensor, thus saving input ports of the CPU.
As described above, there are provided the first series of reluctor corresponding to each cylinder of the internal combustion engine, and the first sensor that detects the leading edge and the trailing edge of the first series of reluctor to generate the leading edge detection pulse and the trailing edge detection pulse, and the polar arc angle and the position of the first series of reluctor corresponding to each cylinder are suitably set, thus the leading edge detection pulse generated by the first sensor may be used as a pulse for determining the ignition timing or injection start timing when each cylinder runs at low speed in the forward rotation and in the reverse rotation of the engine.
Further, as described above, there are provided the second series of reluctor, and the second sensor that detects the leading edge and the trailing edge in the rotational direction of the second series of reluctor to generate the leading edge detection pulse and the trailing edge detection pulse, and the polar arc angle and the position of the second series of reluctor are suitably set, thus the pulse generated by the second sensor may be used as a signal for determining measurement start timing of the ignition timing or determining injection start timing of fuel in the forward rotation and in the reverse rotation.